Peanut Butter Filling
- 3/4 cup unsweetened, salted peanut butter
- 3/4 cup powdered sugar
- 1/2 cup (1 stick) unsalted butter, room temperature
- 1/4 cup unsweetened, salted peanut butter
- 1/2 cup sugar, plus more for rolling
- 1/2 cup light brown sugar (packed)
- 1 large egg
- 1 teaspoon vanilla extract
- 3/4 teaspoon kosher salt
- 1/2 teaspoon baking soda
- 1/2 cup cocoa powder
- 1 cup plus 5 tablespoons all-purpose flour
- Flaky salt, for sprinkling
Stir the jar of peanut butter to incorporate any separated oils. Stick in the freezer for about 15 minutes, or until it’s very firm—imagine the texture of standard, sweetened peanut butter.
Make the filling. Combine the peanut butter and powdered sugar in the bowl of a standing mixer fitted with the paddle attachment. Start on low, then gradually increase the speed to medium-high, until completely smooth. Form the peanut butter mixture into 28 little balls (figure 1 heaping teaspoon each). Stick in the fridge while you make the cookie dough.
Combine the butter, peanut butter, and sugars in the bowl of the standing mixer (no need to clean it out). Cream until light and fluffy, scraping the bowl with a rubber spatula as needed. Add the egg and vanilla. Continue creaming until fluffy, scraping as needed. Add the salt and baking soda. Mix to distribute. Add the cocoa powder. Mix until just incorporated.
Add the flour. Mix until completely incorporated. Form the cookies. Fill a small bowl with white sugar. Use a cookie scoop to scoop 1 tablespoon of chocolate dough. Flatten into a thin patty in your palm. Place 1 peanut butter ball in the center and wrap the chocolate dough around it. Roll around in your palm a few times to smooth out. Roll the ball in the sugar. Place on a plate. Repeat with the remaining chocolate dough and peanut butter filling.
Preheat the oven to 350° F. Fill a cookie sheet with the balls, spaced a few inches apart—figure 9 to 12 per tray. Smush the balls each with a water glass—they don’t spread much, so you want them fairly thin, 1/8 to 1/4 inch. Sprinkle with flaky salt and press in slightly so it adheres. Bake for 8 to 9 minutes, rotating the pan halfway through—they’ll puff up but they shouldn’t crack. Cool slightly, then transfer to a rack to cool completely. Repeat with the remaining cookie dough balls.